There is a system capable of individually recognizing each of objects in a space.
For example, Unexamined Japanese Patent Application Kokai Publication No. 2009-118178 describes as follows.
In a situation where a large number of objects freely move on a floor in a building, a receiver (camera) to perform image sensor communication is disposed on a place with a good view such as a ceiling, and each of the objects emits light modulated according to ID of the object, by as a light emitting diode (LED) or the like.
The receiver receives light emitted from a device to be measured to recognize existence of each ID, thereby a positional relationship between the objects, each being differentiated by each ID.
In such a system, if the objects are, for example, self-propelled moving-objects, it is possible for any one of the objects to see and recognize positions of other objects.